The in vitro hippocampal slice from guinea pig has been utilized to study the effects of pharmacological agents on multi-unit and single neuron activity for the purpose of determining the effects of these substances on the excitability of neurons in the central nervous system. The effects of ethanol on synaptic transmission and the response to applied neurotransmitters are being investigated, as well as the excitability of neurons to direct electrical stimulation. The effects of ethanol on membrane conductance mechanisms is being investigated to determine whether ethanol exerts its effects on excitability through these mechanisms. The necessary characterization of membrane conductances has been performed as the preliminary step of this phase of the study. Effects of ethanol will be compared to those of other neurodepressants including the benzodiazepines and barbiturates.